Synthetic resins have been widely used not only in the form of molded articles but also as containers, packages and packing materials for various products including foods and clothes.
Accordingly, manufacturing of a certain product is accompanied by various plastic wastes at various stages, such as in a manufacturing plant, a distribution system, at the user, etc. Currently, various products are manufactured in order to satisfy consumers' great demands and, therefore, the formation of plastic wastes at every stage is inevitable.
The amount of these plastic wastes, as industrial wastes or general wastes, is more and more increasing and it is well known that manufacturers, distributors and local governments are now confronted with a serious problem of the efficient recovery and treatment thereof.
The same situation applies to expanded materials, such as styrol foam (expanded styrene foam). Because of having excellent properties (lightness, compression strength, moldability, etc.), the expanded styrene foam has been widely applied to, for example, food trays. However, expanded styrene foam is stable and bulky, and does not decompose. Thus, it is a serious problem to efficiently recover expanded styrene foam and to dispose the waste portions thereof.
At present, most industrial wastes are buried in the ground by the waste disposal traders or disposed of by some other methods. On the other hand, general wastes are incinerated or buried in the ground in the waste disposal facilities of local governments.
In any event, plastic wastes contaminate the air and underground water and the disposal thereof may create environmental pollution. As a means for solving these problems, there has been proposed a method for recovering plastic wastes wherein the some are dissolved in hydrocarbon solvents (see, JP-A-5-500186(WO91/03515), JP-A-51-28175 and JP-A-6-32938; the term "JP-A" as used herein means an "unexamined published Japanese patent application"). However, this method is disadvantageous for safety and environmental reasons, since the solvents employed therein (i.e., aromatic hydrocarbons and halogenated hydrocarbons, such as xylene, benzene and carbon tetrachloride) are either poisonous, carcinogenic, or are environmentally disadvantageous.
Accordingly, it is serious problem in this technical field to develop a solvent for recovery which causes no problems of toxicity and safety on the human body, is environmentally safe and yet has high dissolving power for plastic wastes.